No unannounced deal was reached during this week's summit between President Moon Jae-in and US President Donald Trump, the presidential chief of staff said Friday, amid speculation the government could have committed to massive arms purchases from the US during the summit.

"There was no backside agreement whatsoever that can hurt our national interests," Moon's chief of staff Im Jong-seok said during a parliamentary steering committee meeting.

Presidential chief of staff Im Jong-seok (Yonhap

After Tuesday's summit, Trump told a news conference that the South is buying billions of dollars of arms from the US, which led to the main opposition Liberty Korea Party raising speculations that the government might have reached secret arms purchase deals.

But Im said Trump was referring to the arms purchase contracts concluded under previous governments.

"What happened was that there were working-level discussions between the two countries that we're going to carry them (contracts) out," he said. "The issue of state-of-the art assets was left open for future discussion and there was no separate agreement on that."

Im said that Trump's visit to Camp Humphreys, a US military base in Pyeongtaek, helped improve his understanding of the fact that South Korea is making contributions to joint defense. (Yonhap)